During the second round of the Persian-Roman wars that started in 359 A.D., the Iranian army took back the port city of Sukhumi from the occupiers, thus; cleaning Caucasia from Romans. The population of Abkhazia was forcefuly converted to Christianity and Sukhumi was named Sebastopolis. The Romans had destroyed many buldings including the city arc before retreating. Sukhumi was widely used to disembark military units during the expansionist period of the Byzantine Empire. The remains of the city arc have been recently discovered under the Black Sea. Iranians led by Khosrau Anoushirvan left the ruins as they were and added new sections to the city. Abkhazia was made an autonomous Satrapy of the Sassanid Empire in the 7th century Abkhazia retained it's autonomy even after the fall of the Sassanid Empire for a hundred years until Georgia was completely conquered by the Caliph forces. Abkhazia was then conquered by Mongols, Ottomans, and finally Russians. In 1922, it became part of Georgia. Under the Soviets, Armenians were encouraged to migrate to Abkhazia in order to change the demographics, a routine assimilating policy observed under the Bolshevik rule. After disintegration of the U.S.S.R., on July, 23, 1992, Abkhazia declared independence from Georgia